Onset-mitigating high-frequency nerve block

ABSTRACT

A method of blocking signal transmission through a nerve with reduced onset activity includes applying an HFAC to an axon of a nerve to block the transmission of signals through the axon. The method may also include applying a direct current (DC) to the axon, increasing the amplitude of the DC over time to a predetermined amplitude, applying the HFAC, and then decreasing the DC. The method may also include temporarily reducing the amplitude of the HFAC to permit the transmission of signals through the axon and subsequently increasing the amplitude to block transmission without triggering an onset response. The method may also include temporarily applying an unbalanced charge to the nerve and then balancing the charge over time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. patent application Ser. No.15/218,481, filed Jul. 25, 2016, now U.S. Pat. No. 9,884,192, which is adivisional application of U.S. patent application Ser. No. 14/626,992,filed Feb. 20, 2015, now U.S. Pat. No. 9,403,014, which is a divisionalapplication of U.S. patent application Ser. No. 12/739,413, filed Apr.23, 2010, now U.S. Pat. No. 8,983,614, which is a National StageApplication of PCT/US2008/012209, filed Oct. 28, 2008, which claims thebenefit of U.S. Provisional Patent Application No. 60/983,420, filedOct. 29, 2007. The entirety of each of the aforementioned applicationsis hereby incorporated by reference for all purposes.

FEDERAL FUNDING NOTICE

This invention was made with Government support under Grant No.EB002091, awarded by the NIH-National Institute of Biomedical Imagingand Bioengineering. The Federal government has certain rights in thisinvention.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialsubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction of the patent document or the patentdisclosure as it appears in the Patent and Trademark Office patent fileor records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND

Unwanted and/or uncoordinated generation of nerve impulses may be adisabling factor in some medical conditions. For example, uncoordinatedmotor signals may produce spasticity in stroke, cerebral palsy, multiplesclerosis, and other conditions. The uncoordinated signals may result inthe inability to make desired functional movements. Involuntary motorsignals in conditions including tics, choreas, and so on, may produceunwanted movements. Additionally, unwanted sensory signals can causepain. Conventional approaches have attempted to intercept unwanted oruncoordinated nerve impulses along the nerves on which they travel toattempt to reduce and/or eliminate the disabling condition.

Conventional approaches associated with treating these conditions haveproduced unsatisfactory results. For example, drug treatments may haveproduced unwanted side-effects, may have acted globally on the bodyrather than specifically on a specific nerve, and may have been neitherquick acting nor quickly reversible. While chemical treatments (e.g.,Botox, phenol blocks), may be applied more specifically, they may havebeen destructive to the nerve, may have required reapplication, and maynot have been quickly reversible. Other conventional treatments for pain(e.g., transcutaneous electrical nerve stimulation (TENS), implantablepain stimulators) have also produced sub-optimal results.

Both alternating current (AC) and direct current (DC) nerve stimulationare known in the art. The inhibitory effect of high-frequencyalternating current (HFAC) on nerves has been reported since the early1900's. Additionally, DC electrical nerve stimulation has beenillustrated to produce a nearly complete block of nerve activity.However, conventional DC stimulation has damaged both body tissuesand/or electrodes when delivered over prolonged periods of time. Thusconventional DC stimulation has been unsuitable for certainapplications. The damage caused by a DC nerve block is due, at least inpart, to unbalanced charge applied to the nerve, HFAC, which delivers azero net charge to the tissue is likely to be safer as a method fornerve block. However, when HFAC is delivered to a nerve, it causes aburst of activity in the nerve that is undesirable and likely to bepainful. The burst of activity produced by HFAC is referred to as theonset activity.

SUMMARY

This application concerns apparatus, systems, and methods for blockingsignal transmission through a nerve without generating activity in thenerve outside of the system. One example concerns applying a DC and ahigh-frequency alternating current (HFAC) in a combination(s) thatcancels, prevents or minimizes an undesirable reaction of the nerve tothe onset of the HFAC based nerve conduction block.

One example method of blocking nerve signal transmission comprisesapplying a DC at a first amplitude to the axon of a nerve and thenincreasing the amplitude of the DC over a period of time to apredetermined second amplitude. After the DC has reached the secondamplitude, the HFAC is applied. After the HFAC is applied, the amplitudeof the DC is decreased.

Another example method of blocking nerve signal transmission comprisesapplying the HFAC at a first amplitude that blocks signal transmission.The method includes temporarily reducing the HFAC amplitude to permitthe transmission of signals through the axon. The method also includessubsequently selectively increasing the HFAC amplitude to again blocktransmission. In this example, the subsequent blocking occurs withouttriggering an onset response.

Another example method of blocking nerve signal transmission comprisestemporarily applying an unbalanced charge to an axon of a nerve. In oneexample, applying an unbalanced charge may include applying anunbalanced charge AC to the axon and balancing the charge over time. Inanother example, applying an unbalanced charge may include applying anunbalanced charge AC to the axon and varying the amplitude over timewhile also balancing the charge. In another example, applying anunbalanced charge may include applying a DC charge of increasingamplitude and, after reaching a predetermined amplitude, applying anunbalanced AC and gradually increasing the AC amplitude and AC chargebalance over time.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate various example systems, methods,and other example embodiments of various aspects of the invention. Itwill be appreciated that the illustrated element boundaries (e.g.,boxes, groups of boxes, or other shapes) in the figures represent oneexample of the boundaries. One of ordinary skill in the art willappreciate that in some examples one element may be designed as multipleelements or that multiple elements may be designed as one element. Insome examples, an element shown as an internal component of anotherelement may be implemented as an external component and vice versa.Furthermore, elements may not be drawn to scale.

FIG. 1 illustrates an open loop apparatus associated with a nerve block.

FIG. 2 illustrates an open loop apparatus associated with a nerve block.

FIG. 3 illustrates a closed loop apparatus associated with a nerveblock.

FIG. 4 illustrates a closed loop apparatus associated with a nerveblock.

FIG. 5 illustrates a combination of DC and HFAC associated with anonset-mitigating nerve block.

FIG. 6 illustrates a method associated with an onset-mitigating nerveblock.

FIG. 7 illustrates an HFAC associated with an onset-mitigating nerveblock.

FIG. 8 illustrates an HFAC associated with an onset-mitigating nerveblock.

FIG. 9 illustrates an HFAC associated with an onset-mitigating nerveblock.

FIG. 10 illustrates an HFAC associated with an onset-mitigating nerveblock.

FIG. 11 illustrates a method associated with providing a nerveconduction block where an onset response is mitigated.

FIG. 12 illustrates a method associated with providing a nerveconduction block where an onset response is mitigated.

FIG. 13 illustrates an apparatus associated with providing a nerveconduction block where an onset response is mitigated.

DETAILED DESCRIPTION

Example systems, methods, and apparatus produce a nerve block using HFACwaveforms. The block produced by HFAC waveforms is a conduction block inthe nerve, and not simply a fatigue block. The block may be referred toas a “nerve conduction block”. The block is not a result of the nervebeing stimulated until it is too fatigued to respond and can no longerrecover before the next pulse. The HFAC waveforms block conductionthrough the nerves by blocking signal transmission through the axon.Unlike a chemical block, which interrupts the transmission of a chemicalsignal from the ends of one nerve to the ends of another, an HFAC nerveconduction block prevents the axon of the nerve from transmitting anysignals past the area of the block. The block is based on how electricalcurrents produce activation or block nerve conduction through theirinfluence on the voltage-gated ion channels in the nerve membrane.

HFAC waveforms depolarize the nerve membrane causing the inactivationgates to close. The biophysical mechanism that produces the onsetresponse is based on the effect of the depolarizing current on the nervemembrane. In general, depolarizing the nerve membrane triggers theopening of the fast sodium ion channels, initiating an action potential.Placing the nerve in an alternating current depolarizing field, however,actually results in conduction failure, because it forces theinactivation sodium ion gate to remain closed. Therefore, depolarizationis involved in both activating and blocking nerve conduction. It is thisdichotomy of action that produces the onset response.

There are two phases of the onset response. The first phase is asummated twitch response that occurs in those nerve fibers to which anAC near or above the block threshold is being applied. The “blockthreshold” is defined as the voltage below which a complete block is notobtained. The block threshold increases with frequency. The blockthreshold generally varies inversely with axon diameter. In addition,the block threshold varies approximately as the square of theperpendicular distance to the axon from the electrode. When theelectrode is closer than one millimeter to the axon, the electrodeposition along the length of the axon also affects the amplitude of theblock threshold.

Once the initial firing is over, which generally occurs in approximately20 milliseconds, these axons are blocked. The second phase is a periodof repetitive firing that can last many seconds. This second phase isnot always present and tends to be significantly reduced with higheramplitudes of HFAC. This second phase may be due to the repetitivefiring of axons that are on the fringes of the current spread from theelectrode. Eventually, the firing in these fibers comes to a stop. Theamplitude of the electrical signal decreases with distance from theelectrode. A decrease in the second phase at higher amplitudes may berelated to higher amplitudes placing more of the nerve fiber completelywithin the region that provides sufficient amplitude to produce theblock. Since the current gradients are sharper, fewer fibers are withinthe amplitude region that produces repetitive firing.

Eliminating the undesired onset entirely involves eliminating bothphases of the onset response. The repetitive phase can be reduced byadjusting amplitude and frequency. For example, a 30 kilohertz, 10 voltspeak-to-peak sinusoidal waveform may eliminate the repetitive phase.Generally it is not possible to eliminate the entire onset response bychanging frequency and amplitude alone.

Recall that the damage caused by a DC nerve block is due to the chargeimbalance applied to the nerve. Therefore, example systems, methods, andapparatus balance charge using AC. Balancing the charge prevents and/orminimizes damage caused by unbalanced charges. A pure AC nerve blocktypically produces an onset response from the nerve on start-up. Thussome examples described and claimed herein first apply DC to a nerve andthen subsequently apply an HFAC nerve block. The combination of DC andHFAC is crafted to prevent the occurrence of the onset response in thenerve to be blocked. Conventional approaches employing an HFAC waveformas a nerve conduction block produce the onset response that is typicallyunacceptable in the application of HFAC waveforms to human patients.

“High-frequency”, as used herein with reference to alternating current(e.g., HFAC), refers to frequencies above approximately 1 kiloHertz. Insome examples, high-frequency refers more specifically to 5 to 50kiloHertz. Example systems, methods, and apparatus described hereinemploy a waveform having an amplitude of approximately 4 to 10 volts perpulse. Example systems, methods, and apparatus described herein employ awaveform having a current of about 1 milliamp to about 12 milliamps.Within these voltage and amperage ranges, a waveform having a higherfrequency will generally require a higher amplitude to provide aneffective block.

Examples described herein may have application in areas including motornerve block, sensory nerve block, and autonomic block. Additionally,examples described herein may be applied in an open loop configurationwhere the block is controlled through a switch and/or in a closed loopconfiguration where the block is controlled automatically through asensor(s).

FIG. 1 illustrates an example apparatus 20 associated with blockingtransmission in a nerve. Apparatus 20 includes an electrode 22 connectedto a controller 24 suitable for delivering HFAC and/or both DC and HFACsignals to a nerve 26. Apparatus 20 has an open loop configuration wherethe controller 24 includes a switch to control application of the block.This configuration of apparatus 20 may facilitate controlling, forexample, muscle spasticity. Apparatus 20 may apply the HFAC through aset of HFAC electrodes 22 on the motor branches of the nerve 26. Thisfacilitates targeting a specific muscle associated with nerve 26 tofacilitate relaxing that muscle. In one example, apparatus 20 mayprovide a sternocleidomastoid block useful for treating torticollis.

FIG. 2 illustrates an apparatus 30 used, for example, to block neuromapain, pain associated with a missing appendage, pain associated with adamaged appendage, and so on. Apparatus 30 may, therefore, produce amedian nerve block. Apparatus 30 comprises an HFAC blocking electrode 32and an implantable controller 34. The blocking electrode 32 may bepositioned adjacent to a nerve proximal to a neuroma. In thisapplication, the nerve block can be delivered continuously, can betriggered using an external signal device 36, and so on.

FIG. 3 illustrates an apparatus 40 that provides a motor block. Themotor block may be triggered by a recorded signal. Apparatus 40 is aclosed-loop system and is illustrated in an application to blockintractable hiccups. Indicia (e.g., biological signals) associated withan impending hiccup may be recorded via a sensor 42. In one example, theindicia may appear as a large signal on the phrenic nerve. This signalmay control triggering a controller 44 to apply an HFAC block to thephrenic nerve. The block may be administered using an electrode 46adjacent to the phrenic nerve. The HFAC block prevents diaphragmcontraction for a brief period, which interrupts and/or preempts signalsthat cause the diaphragm to hiccup.

Signals associated with moving a muscle may be recorded when a userintends to move that muscle. The signals may be propagated along anerve. These signals may facilitate controlling spastic muscles instroke patients, patients having multiple sclerosis, patients havingcerebral palsy, and so on. In one example, signals may be recorded fromboth spastic muscles and non-spastic muscles. Therefore, FIG. 4illustrates an apparatus 50 that includes a controller 52. Controller 52comprises a recorder for recording and processing signals from sensors54 in muscles 56 and/or nerves that control muscles 56. The controller52 controls a signal generator 58 to apply an HFAC waveform to anelectrode 60 adjacent a nerve that controls muscles 56.

Spasticity reduces function in muscles. However, improved function maybe achieved by producing a partial block of undesired motor activity.Thus, example apparatus, methods, and so on, may be configured toquickly reverse an HFAC block. In one example, improved function may beachieved by combining an HFAC block with an intelligent control systemthat varies the nerve block based on sensed activity including, forexample, nerve activity, muscle activity, and so on.

Example systems, methods, and apparatus may produce at least threecategories of no-onset and/or onset-mitigating HFAC block solutions. Ina first example, separate “onset-blocking” electrodes apply a DC blockon either side of the HFAC electrodes. In a second example,charge-balanced transitory variations of a HFAC waveform produce ano-onset and/or onset-mitigating HFAC block. In a third example,charge-imbalanced transitory variations of the HFAC waveform produce ano-onset and/or onset-mitigating HFAC block.

FIG. 5 illustrates a combination of a DC waveform 510 and an HFACwaveform 520 to produce an HFAC block. In one example, the DC waveform510 and the HFAC waveform 520 are provided using separate electrodes. Inone example, DC waveforms and HFAC waveforms are provided through asingle set of electrodes. The charge in the DC waveform 510 is ramped upin region 512 before the HFAC waveform 520 is turned on. The DC waveform510 in region 514 has amplitude sufficient to provide a DC block, whichwill block the onset response from the HFAC waveform 520. The DCwaveform 510 is ramped down in region 514 once the onset activity iscomplete. Unlike the charge-imbalanced waveforms discussed below, thisramped DC waveform 510 allows the onset activity caused by the HFACwaveform 520 to occur, but prevents that onset activity frompropagating. Although continuous delivery of DC at this level can damagethe electrodes that deliver the DC and nearby tissue, infrequent briefapplication of the DC block may not cause such damage. In one example,the DC block is delivered for approximately 100 to 200 milliseconds eachtime the HFAC block is turned on. Since a DC block can be produced bymonopolar electrodes, in one example the DC electrodes and the HFACelectrodes may be combined into a single five-pole nerve cuff electrode.This five-pole nerve cuff electrode may include two outer electrodes fordirect current and three inner electrodes for HFAC. A further form ofthe electrode may utilize a three-pole nerve cuff electrode in which theDC and HFAC are superimposed on the outer electrodes.

FIG. 6 illustrates a method associated with onset-mitigating HFAC.Method 600 includes, at 610, applying a first waveform to a nerve toalter onset activity in that nerve. Method 600 also includes, at 620,applying a second transitory wave to the nerve. Method 600 alsoincludes, at 630, applying a third steady state wave to the nerve tocontinue the HFAC block in the nerve.

FIG. 7 illustrates a charge-balanced approach that includes applying arapid onset block above the block threshold and accepting the initialonset response. In this approach, the amplitude is then lowered belowthe block threshold but maintained high enough to avoid the zone ofrepetitive firing. The previously blocked nerve can conduct normallythrough the region of HFAC delivery at this amplitude. Then, when ablock is desired, the amplitude is ramped up to the block threshold. Inthis example, the block can be achieved without further firing and thuswith no additional onset response. This method maintains a zero netcharge but requires that the waveform be delivered even when a block isnot needed. In this example, the onset still occurs when the system isfirst turned on. This method may be employed, for example, in strokeapplications. In this environment there may be periods of rapidmodulation of the block during functional tasks. Thisamplitude-modulation method may be suitable in this environment becauseit can produce a quick transition between block and no-block conditions.During periods of inactivity, the block can be turned off. However theblock can be re-initiated prior to activity using one of theonset-blocking alternatives.

FIG. 8 illustrates applying an HFAC waveform 810 with an initial offsetcharge. The HFAC waveform 810 is then ramped up to a charge-balancedaverage. This type of charge-imbalanced transitory variation mayeliminate the onset response. The HFAC waveform 810 is initiallycharge-imbalanced, and then transitions to a charge-balanced waveformover a period of tens of milliseconds or longer. This achieves a briefperiod of effective direct current. In FIG. 8, both the amplitude of theHFAC waveform 810 and the amount of offset are ramped toward thecharge-balanced waveform.

FIG. 9 illustrates another HFAC waveform 910 for producing a nerveblock. This is a second example that uses charge-imbalanced waveforms toeliminate and/or mitigate the onset response and relies on the virtualelectrode zones that develop during monophasic activation. Forsufficiently large depolarizing monophasic pulses, the initial actionpotentials associated with an onset response are blocked in the adjacentvirtual anodes. This may be referred to as an anodal surround block.Using this feature, the HFAC block will start with a monophasic waveformthat produces an anodal surround block starting with the first pulsedelivered. Subsequently, the charge-imbalance is decreased to achievebalance. The steady state condition is a charge-balanced HFAC waveformthat maintains the block. The transitory portion of this waveform lastsapproximately 100 milliseconds or longer and is robust across axondiameters and electrode distances.

FIG. 10 illustrates another waveform 1010 for producing a nerve block.Waveform 1010 starts with a ramped cathodic or anodic direct current.While the term “ramped” is used herein, one skilled in the art willappreciate that more generally the waveform may include linear and/ornon-linear increases in DC and/or HFAC amplitude. Thus, “ramped” or“ramping” are not to be interpreted as requiring a linear increase up tosome level. An HFAC waveform is started after a period where the rampeddirect current is applied. The HFAC waveform has its amplitude increaseduntil it reaches a block threshold. At this point, the DC offset isramped down until the whole waveform is charge-balanced, thus allowingthe HFAC block to be established without onset action potentials. In oneexample, the DC offset peak is in the range of approximately ten percentof the HFAC amplitude. In one example, the total time during which theDC is applied is about 80 milliseconds. The total time includes the DCramp-up, the DC plateau, and the DC ramp down.

Some portions of the detailed descriptions that follow are presented interms of algorithms. These algorithmic descriptions and representationsare used by those skilled in the art to convey the substance of theirwork to others. An algorithm, here and generally, is conceived to be asequence of operations that produce a result. The operations may includephysical manipulations of physical quantities. The physicalmanipulations create a concrete, tangible, useful, real-world result.

Example methods may be better appreciated with reference to flowdiagrams. For purposes of simplicity of explanation, the illustratedmethodologies are shown and described as a series of blocks. However, itis to be appreciated that the methodologies are not limited by the orderof the blocks, as some blocks can occur in different orders and/orconcurrently with other blocks from that shown and described. Moreover,less than all the illustrated blocks may be required to implement anexample methodology. Blocks may be combined or separated into multiplecomponents. Furthermore, additional and/or alternative methodologies canemploy additional, not illustrated blocks.

FIG. 11 illustrates a method 1100 associated with an HFAC nerveconduction block. Method 1100 includes, at 1110, applying a first HFACto an axon of a nerve. The first HFAC will have a first amplitude, afirst frequency, and a first current. The combination of amplitude,frequency, and current is configured to produce a nerve conduction blockin the axon. Recall that a nerve conduction block actually blockstransmission of signals through the axon.

Method 1100 also includes, at 1120, applying a second HFAC to the axon.The second HFAC has a second amplitude, a second frequency, and a secondcurrent. This combination of amplitude, frequency, and current will notproduce a nerve conduction block in the axon. However, this combinationof amplitude, frequency, and current will prevent the occurrence of anonset condition in the axon upon the application of a third HFAC that issufficient to produce a nerve conduction block in the axon. One skilledin the art will appreciate that the third HFAC may be similar to oridentical to the first HFAC.

Thus, method 1100 also includes, at 1130, applying a third HFAC to theaxon. The third HFAC has a third amplitude, a third frequency, and athird current. This combination of the third amplitude, the thirdfrequency, and the third current will produce a nerve conduction blockin the axon. However, it will do so with less onset activity than wouldotherwise be incurred.

In one example, all three frequencies are in the range of 1 kiloHertz to100 kiloHertz. In one example, the first and third frequencies are thesame, and the second frequency is different. In one example, the firstamplitude and the third amplitude are in the range of 4 voltspeak-to-peak to 10 volts peak-to-peak. In one example, the first currentand the third current are in the range 1 milliamp to 12 milliamps. Oneskilled in the art will appreciate that various combinations offrequency, amplitude, and current can produce a nerve conduction block.The nerve conduction block may be, for example, a motor nerve block, asensory nerve block, an autonomic block, and so on. The nerve conductionblock may be applied to treat symptoms of torticollis, neuroma pain,hiccups, cerebral palsy, muscular dystrophy, stroke, and so on. Thenerve conduction block may be, for example, a sternocleidomastoid block,a median nerve block, a phrenic nerve block, a modulated spasticityblock, and so on.

Method 1100 may be controlled to selectively apply the first HFAC, thesecond HFAC, and/or the third HFAC based, at least in part, on a controlsignal received from an open loop control apparatus. The control signalmay be received, for example, from a switch. Similarly, method 1100 maybe controlled to selectively apply the first HFAC, the second HFAC,and/or the third HFAC based, at least in part, on a control signalreceived from a closed loop control apparatus. The closed loop controlapparatus may be, for example, a sensor. Method 1100 may also becontrolled to selectively alter the frequency, voltage, and current ofan HFAC based on inputs from an open loop apparatus and/or a closed loopapparatus.

In different examples, the first HFAC, the second HFAC, and/or the thirdHFAC may initially be unbalanced with respect to charge. Thus, method1100 may include balancing, over a period of time, the charge of aninitially unbalanced HFAC. In one example, method 1100 may includevarying the amplitude of the unbalanced HFAC over time while the chargeis being balanced.

FIG. 12 illustrates a method 1200 associated with an HFAC nerveconduction block. Method 1200 includes, at 1210, first applying a directcurrent (DC) to an axon of a nerve. This DC will have a first DCamplitude that is not sufficient to produce a nerve block in the axon.Method 1200 then proceeds, at 1220, to increase the first DC amplitudeover a period of time. The first DC amplitude is increased to a secondDC amplitude that is sufficient to produce a nerve block in the axon.

Method 1200 then proceeds, at 1230, to apply an HFAC to the axon. TheHFAC has an HFAC amplitude, an HFAC frequency, and an HFAC current. Thecombination of frequency, amplitude, and current is designed to producea nerve conduction block in the axon. Note that the HFAC is appliedafter the DC has been ramped up to a desired level. Method 1200 thenproceeds, at 1240, to decrease the second DC amplitude to a third DCamplitude over a period of time. The DC having the third DC amplitude isnot sufficient to produce a nerve block in the axon. Thus, method 1200provides a combination of the DC and the HFAC in an order that reducesan onset activity that is observed in the nerve either proximally ordistally to the blocking electrode or electrodes.

In one example, the DC offset peak is between five percent and fifteenpercent of the HFAC amplitude. In one example, the first period of timeand the second period of time during which the DC is ramped up and thenramped down collectively comprise less than 80 milliseconds. In anotherexample, the first period of time is between 100 milliseconds and 200milliseconds, and the second period of time is between 100 millisecondsand 200 milliseconds.

FIG. 13 illustrates an apparatus 1300 associated with an HFAC nerveconduction block. Apparatus 1300 includes an electrode 1310 and awaveform generator 1320 connected to the electrode. Apparatus 1300 alsoincludes a controller 1330. Controller 1330 is to control the waveformgenerator 1320 to apply DC and/or HFAC as described in connection withmethod 1100 (FIG. 11) and/or method 1200 (FIG. 12). In one example,apparatus 1300 may include a switch 1340 to selectively control thecontroller 1330 and/or the waveform generator 1320. In another example,apparatus 1300 may include a sensor 1350 to selectively control thecontroller 1330 and/or the waveform generator 1320. In one example, theelectrode 1310 may have five nodes. The five nodes may include a set oftwo inner nodes for applying an HFAC and a set of three outer nodes forapplying a DC.

References to “one embodiment”, “an embodiment”, “one example”, “anexample”, and so on, indicate that the embodiment(s) or example(s) sodescribed may include a particular feature, structure, characteristic,property, element, or limitation, but that not every embodiment orexample necessarily includes that particular feature, structure,characteristic, property, element or limitation. Furthermore, repeateduse of the phrase “in one embodiment” does not necessarily refer to thesame embodiment, though it may.

While example systems, methods, and so on have been illustrated bydescribing examples, and while the examples have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe systems, methods, and so on described herein. Therefore, theinvention is not limited to the specific details, the representativeapparatus, and illustrative examples shown and described. Thus, thisapplication is intended to embrace alterations, modifications, andvariations that fall within the scope of the appended claims.

To the extent that the term “or” is employed in the detailed descriptionor claims (e.g., A or B) it is intended to mean “A or B or both”. Whenthe applicants intend to indicate “only A or B but not both” then theterm “only A or B but not both” will be employed. Thus, use of the term“or” herein is the inclusive, and not the exclusive use. See, Bryan A.Gamer, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).

To the extent that the phrase “one or more of, A, B, and C” is employedherein, (e.g., a data store configured to store one or more of, A, B,and C) it is intended to convey the set of possibilities A, B, C, AB,AC, BC, ABC, AAA, AAB, AABB, AABBC, AABBCC, and so on (e.g., the datastore may store only A, only B, only C, A&B, A&C, B&C, A&B&C, A&A&A,A&A&B, A&A&B&B, A&A&B&B&C, A&A&B&B&C&C, and so on). It is not intendedto require one of A, one of B, and one of C. When the applicants intendto indicate “at least one of A, at least one of B, and at least one ofC”, then the phrasing “at least one of A, at least one of B, and atleast one of C” will be employed.

What is claimed is:
 1. A closed-loop nerve block system, the systemcomprising: at least one sensor to detect a signal from a biologicalcomponent, wherein the signal is indicative of a biological process; acontroller coupled to the at least one sensor and configured to receivean indication of the signal from the at least one sensor, the controllerfurther comprising a processor to determine whether nerve block isrequired by the biological process based on the indication of the signalfrom the at least one sensor; a waveform generator coupled to thecontroller to generate a nerve block signal when the controller sendsinstructions that the nerve block is required based on the biologicalprocess; and one or more electrodes coupled to the waveform generatorand configured to apply the nerve block signal to a nerve associatedwith the biological process, wherein the one or more electrodescomprises at least two electrode contacts, wherein the nerve blocksignal comprises a first waveform delivered to one of the at least twoelectrode contacts and a second waveform delivered to another of the atleast two electrode contacts, wherein: the first waveform is appliedthrough one of the at least two electrode contacts for a first time; thefirst waveform is applied through the one of the at least two electrodecontacts and the second waveform is applied through the other of the atleast two electrode contacts together for a second time, wherein thesecond time is sufficient for the first waveform to block an onsetresponse associated with application of the second waveform; and thesecond waveform is applied through the other of the at least twoelectrode contacts for a third time.
 2. The system of claim 1, whereinthe biological process is related to at least one of torticollis,neuroma pain, hiccups, muscular dystrophy, cancer pain, post-operativepain, chronic pain, pain, and stroke.
 3. The system of claim 1, furthercomprising at least two sensors, each to detect different signals fromone or more biological components.
 4. The system of claim 3, wherein thecontroller is coupled to the at least two sensors and the processordetermines whether nerve block is required by the biological processbased on indications of the different signals from the at least twosensors.
 5. The system of claim 4, wherein the one or more electrodeseach comprises at least two contacts, and the controller instructs arespective one of the at least two contacts to apply the nerve blocksignal based on the indications of the different signals from the atleast two sensors.
 6. The system of claim 1, wherein the nerve block isone or more of an efferent neuron block, an afferent neuron block, andan interneuron block.
 7. The system of claim 1, wherein the controllersignals a switch between the waveform generator and the electrode toclose when the controller determines that nerve block is required by thebiological process.
 8. The system of claim 7, wherein the controllersignals the switch to open after expiration of a time for application ofthe block.
 9. The system of claim 1, wherein the controller isconfigured to adjust one or more of the frequency, voltage and currentof the nerve block signal based on the signal from the biologicalcomponent.
 10. The system of claim 1, wherein the at least one sensor isconfigured to detect the signal from a biological component comprisingexcitation of the nerve.
 11. The system of claim 1, wherein the waveformgenerator is configured to generate a nerve block signal having acurrent of between 1 milliamp and 12 milliamps.
 12. A closed-loop nerveblock method, the method comprising: detecting, by a sensor, a signalfrom a biological component, wherein the signal is indicative of abiological process; receiving, by a controller, an indication of thesignal from the at least one sensor; automatically determining, by thecontroller, whether nerve block is required by the biological processbased on the indication of the signal from the at least one sensor; inresponse to the controller indicating the nerve block is required by thebiological process, configuring, by a waveform generator, a nerve blocksignal in response to instructions from the controller indicating thatthe nerve block is required by the biological process; and applying, byone or more electrodes, the nerve block signal to a nerve associatedwith the biological process, wherein the one or more electrodescomprises at least two electrode contacts, wherein the nerve blocksignal comprises a first waveform delivered to one of the at least twoelectrode contacts and a second waveform delivered to another of the atleast two electrode contacts, wherein: the first waveform is appliedthrough one of the at least two electrode contacts for a first time; thefirst waveform is applied through the one of the at least two electrodecontacts and the second waveform is applied through the other of the atleast two electrode contacts together for a second time, wherein thesecond time is sufficient for the first waveform to block an onsetresponse associated with application of the second waveform; and thesecond waveform is applied through the other of the at least twoelectrode contacts for a third time.
 13. The method of claim 12, whereinthe biological process is related to at least one of torticollis,neuroma pain, hiccups, muscular dystrophy, cancer pain, post-operativepain, chronic pain, pain, and stroke.
 14. The method of claim 12,wherein the nerve block is one or more of an efferent neuron block, anafferent neuron block, and an interneuron block.
 15. The method of claim12, further comprising signaling, by the controller, a switch betweenthe waveform generator and the electrode to close when the controllerdetermines that nerve block is required by the biological process. 16.The method of claim 15, further comprising signaling, by the controller,the switch to open after expiration of a time for application of theblock.
 17. The method of claim 12, further comprising adjusting one ormore of the frequency, the amplitude and a current of the nerve blocksignal based on the signal from the biological component.
 18. The methodof claim 12, wherein detecting the signal from the biological componentcomprises detecting excitation of the nerve.
 19. A closed-loop nerveblock system for treating pain, the system comprising: at least onesensor to detect a signal from a nerve related to pain; a controllercoupled to the at least one sensor and configured to receive anindication of the signal from the at least one sensor; a processorcoupled to the controller, the processor configured to triggerapplication of a nerve block signal based on the signal detected by theat least one sensor; a waveform generator coupled to the controllerconfigured to generate the nerve block signal when the controller sendsinstructions that the nerve block is required based on the biologicalprocess; and one or more electrodes coupled to the waveform generatorand configured to apply the nerve block signal to the nerve associatedwith the biological process, wherein the one or more electrodescomprises at least two electrode contacts, wherein the nerve blocksignal comprises a first waveform delivered to one of the at least twoelectrode contacts and a second waveform is delivered to another of theat least two electrode contacts, wherein: the first waveform is appliedthrough one of the at least two electrode contacts for a first time; thefirst waveform is applied through the one of the at least two electrodecontacts and the second waveform is applied through the other of the atleast two electrode contacts together for a second time, wherein thesecond time is sufficient for the first waveform to block an onsetresponse associated with application of the second waveform; and thesecond waveform is applied through the other of the at least twoelectrode contacts for a third time.